Spinning process



Patented Oct. 7, 1945 SPINNING PROCESS Del., asaignor topanagel. Wilmington, B. I. du Pont de Nemours i Company, Wilmington, Del.. a corporation of Delaware tlon llareh 3 1, 194:,

No Drawing.

Appllea serial No. 481,287

7 Clalllaa- (CI. 18-54) This invention relates to the production of fine denier filaments and muitifiiament yarns and threads composed of a synthetic linear polymer. More particularly, this invention relates to the production of such filaments, yarns and threads containing incorporated therein a finely divided, inert material in an amount less than that which will produce a substantially visible delusterins or dulling eilect. whereby the rupturing of the filaments or yarn, during the coid-drawins thereof, will be materially diminished.

The melt-spinning and cold-drawing (that is, drawing under tension in the solid state) of synthetic linear polymers is well known in the art. The U. B. patents to Carothers Nos. 2,071,250, 2,071,201, 2,071,253 and 2,180,048 all disclose the melt-spinning and cold-drawing oi synthetic linear polymers including polyamides, polyesters, polyethers and polyanhydrides as well as mixed polymers or interpolymers, for example polyamide-polyesters. Of these polymers, the most interesting and useful are the synthetic linear polyamides, more particularly described in the last two above mentioned patents. It is also well known that other synthetic linear polymers, for xample vinylidene dichloride polymers, acrylonitrile polymers and interpolymers of vinyl acetate and vinyl chloride can be melt spun and cold-drawn.

The present invention in its broad aspects is applicable to the melt spinning and cold-drawing of any fiber-forming synthetic linear polymer.

The cold drawing of synthetic linear polymer yarn is usually done by feeding the yarn from one pair oi positively driven rollers to a second pair of positively driven rollers rotating at a suitably higher speed than said first pair. Preferably, the draw tension is concentrated at a precise point between the pairs of rollers to prevent wandering of the draw-point.

As might be expected. the cold-drawing of yarns composed of fine denier filaments which involves the stretching of the filaments from 200% up to 500%, or more, presents many problems. One of these is the tendency of the filaments and in some cases the entire yarn to break with the consequent production of inferior yarn. As might be expected, this happens more frequently as the filament denier is decreased and as the degree of drawing is increased. In the production oi. bright. i. e. substantially undelustered, synthetic linear polyamide hosiery yarn, the breakage of filaments and yarns has been so high as to be a cause of real concern.

It is therefore an object of this invention to thetic linear polymer which can be readily colddrawn without excessive breakage of yarns and filaments.

It is another object of this invention to improve th melt spinning of bright, fine denier filaments and multifilament yarns from a synthetic linear polymer in such a manner as to reduce the breakage of said yarns and filaments in the subsequent cold-drawing thereof.

Other objects of the invention will appear here- The objects of the invention may be accomplished, in general, by producing bright, colddrawable, fine denier filaments and multifilament yarns composed of a synthetic linear polymer containing, homogeneously dispersed throughout the body thereof. a finely divided, inert material in an amount substantially less than that which will produce a visible delustering efiect. The preferred procedure for accomplishing this is to prepare a melt of a synthetic linear polyamlde containing from 0.005% to 0.05% by weight of the finely divided, inert material, for example titanium dioxide, and melt spinning the polyamide in a known manner.

The addition oi finely divided, inert material, for example pigments and pigment-like material, to synthetic linear polymer filament-forming compositions is, of course. well known. Conventionally. this is done to produce opaque or low luster yarns idelustered yarns). with other yarns, it has however also been done for such purposes as to produce staple yarn having good cohesion, or to produce yarn having low running tension in textile q pment.

There is nothing in the above mentioned, previously known processes which would suggest that the addition of less than 0.05% of a finely divided. inert material to a synthetic linear polymer melt will, upon melt spinning, produce filaments and yarns which can be cold-drawn with decidedly fewer filament and yarn breaks than in the absence of said finely divided, inert material. Such a minute amount of inert material is definitely lnsuiliclent to accomplish the objects and purposes of the above mentioned, previously known processes.

It is known that the presence of finely divided, inert material such as titanium dioxide tends to weaken yarn. It is also known that the colddrawing operation, in view of the high tension employed, is very critical. It would. therefore, be supposed that the cold-drawing of yarn containing such a finely divided. inert material would result in increased breakage of yarns and filaments.

The following specific examples are given to illustrate preferred method; of carrying out the present invention. It is ever that these examples are not to be considered as llmitative of the scope of the invention.

Example I to be understood how- The yarn was not visibly delustered.

A similar polyhexamethylene adipamide polymer of relative viscosity 33.5 (determined by the method described below). but containing no titanium dioxide was spun from melt to form a Gil-filament yarn. The yarn was subsequently cold-drawn at a draw ratio or 4.40 to produce a 210 denier-60 filament yarn with a. tenacity of 6.5 grams per denier and an elongation 01' 14%.

ror test showed yards of yarn.

Example I! Polyhexamethylene adipamide polymer of relatlve viscosity 34 (determined by the method described below) and containing 0.05% by weight A similar polyhexamethylene adipamide oi relative viscosity 34 (determined by the method described below). but containing no titanium dioxide was melt spun to form a 69-fiiament yarn which was subsequently cold drawn at a draw ratio of 4.40 to produce a 210 denier-68 filament yarn with a tenacity of 6.5 grams per denier and an elongation oi 14%. In the drawing operation here were several complete yarn breaks and a creel mirror test showed seventy broken filaments per 1,000 yards of yarn.

A second sample oi the polymer mentioned in the previous paragraph was melt spun to form The yarn was subsequently yards of yarn.

The above two examples show two very important advantages which follow the teachings oi the present Invention. In the first place, the presence oi a small amount of titanium dioxide in the olymer as spun makes it possible to draw bright yarn without the occurrence. during the drawing. of too many yarn breaks and broken filaments for acceptable plant production. In the presence or a small amount broken ends were not decreased. Consequently, the titanium dioxide eil'ect is not a draw ratio eiiect. Conversely, it shows that yarn containin: small amounts of titanium dioxide can be ratio to end with the same (desired) elongation and thereiore increas the productivity oi the s machines.

While the examples show a preference for a relative viscosity oi 88.5 to 84.0, the relative Viscosity may be between 15 and 80.

The term "relative the synthetic linear poly pleteiy soluble in 00% formic acid is used in this determination.

culated as the ratio of the two.

In the examples. the melt and colddrawing of poivhexamethylene adipenude ram Similarly, the invention is not limited to the use of titanium dioxide. but

are conventionally used in practically all operating plants.

Quantities of 0.01% to 0.03% of titanium dioxide, based on the weight of the polyamide, are preferred. The quantities of 0.005% to 0.05% weight are effective to produce the desired results while at the same time permitting the production of bright filaments and yarn and the term "bright" is intended to signify filaments and yarn having a brightness not less than that which is incident to the use of said quantities of titanium dioxide. One skilled in the art can quite readily determine the optimum proportion of any other finely divided, inert material which may be used instead 01' the titanium dioxide.

By the term "finely divided, inert material" is meant a material which has no chemical action on said polymer and which is in a state of division of the order of yarn delustering or pismenting material.

The invention described herein has importantly advanced the art of producing cold-drawn. bright filaments and yarns composed of a synthetic linear polymer, thereby permitting maximum production of excellent yarn with existing equipment. It has now been found that, by the practice of this invention, the number of yarn and filament breaks during cold-drawing is decreased and a larger percentage of production can now be classified as completely satisfacwry run. It has been found too that bright yarn can be produced having the desired high tenacity (highly drawn yarn) and fine denier per filament.

A surprising and unexpected result of the invention is that the yarn produced in accordance 'with this invention is not nearly so wild" on a yarn.

Since it is obvious that many changes and modifications can be made in the above described details without departing from the nature and spirit of the invention, it is to be understood that theinventionisnottobelimitedtotheabove said details except as set forth in the appended claims.

Iclaim:

1. The process of reducing the breakage of cold-drawable filamentous structures composed of a synthetic linear polyamide which comprises preparing a composition containing said polyamide and a finely divided, inert material homogeneously dispersed therein in an amount from 0.005 to 0.05%, spinning a filamentous structure from said composition and cold-drawing said structure.

2. The process of reducing the breakage of cold-drawable filamentous structures composed of a synthetic linear polyamide which comprises preparing a melt of said poiyamide containing a finely divided, inert material homogeneously dispersed therein in an amount from 0.005% to 0.05%, spinning a filamentous structure from said melt and cold-drawing said structure.

3. The process of reducing the breakage of cold-drawable filamentous structures composed of polyhexamethylene adipamide which comprises preparing a melt of said polymer containing a finely divided, inert material homogeneously dispersed therein in an amount from 0.005% to 0.05%, spinning a filamentous structure from said melt and cold-drawing. said structure,

4. An unoriented, cold-drawable, filamentous structure composed of a synthetic linear polyamide containing, homogeneously dispersed throughout the body thereof, a finely divided. inert material in an amount from 0.005% to 0.05%.

5. An unoriented, cold-drawable, filamentous structure composed oi polyhexamethylene adipamide containing, homogeneously dispersed throughout the body thereof. a finely divided. inert material in an amount from 0.005% to 0.05%.

6. The process of reducing the breakage of cold-drawable filamentous structures composed of a synthetic linear polyamide which comprises prep a melt of said polyamide containin finely divided titanium dioxide homogeneously dispersed therein in an amount from 0.005% to 0.05%, spinning a filamentous structure from said melt and cold drawing said structure.

I. ran unoriented, cold-drawable, filamentous structure composed of a synthetic linear polyamide containing homogeneously dispersed throughout the body thereof finely divided titanium dioxide in an amount from 0.005% to 0.05%.

EDGAR W. BPANAGEL. 

